object App {
def main(args: Array[String]) {
val conf = new spark.SparkConf().setMaster("local[2]").setAppName("mySparkApp")
val sc = new spark.SparkContext(conf)
val sqlContext = new SQLContext(sc)
val jdbcUrl = "1.2.34.567"
val jdbcUser = "someUser"
val jdbcPassword = "xxxxxxxxxxxxxxxxxxxx"
val tableName = "myTable"
val driver = "org.postgresql.Driver"
Class.forName(driver)
val df = sqlContext
.read
.format("jdbc")
.option("driver", driver)
.option("url", jdbcUrl)
.option("userName", jdbcUser)
.option("password", jdbcPassword)
.option("dbtable", tableName) // NullPointerException occurs here
.load()
}
}
我想从 Spark 连接到 LAN 上的 Postgres 数据库。运行时出现如下错误:
Exception in thread "main" java.lang.NullPointerException
at org.apache.spark.sql.execution.datasources.jdbc.JDBCRDD$.resolveTable(JDBCRDD.scala:71)
at org.apache.spark.sql.execution.datasources.jdbc.JDBCRelation$.getSchema(JDBCRelation.scala:210)
at org.apache.spark.sql.execution.datasources.jdbc.JdbcRelationProvider.createRelation(JdbcRelationProvider.scala:35)
at org.apache.spark.sql.execution.datasources.DataSource.resolveRelation(DataSource.scala:318)
at org.apache.spark.sql.DataFrameReader.loadV1Source(DataFrameReader.scala:223)
at org.apache.spark.sql.DataFrameReader.load(DataFrameReader.scala:211)
at org.apache.spark.sql.DataFrameReader.load(DataFrameReader.scala:167)
at <redacted>?.main(App.scala:42)
at <redacted>.App.main(App.scala)
option("dbtable", tableName)
行出现空指针异常是否有明显的原因?我正在使用 Spark-2.3.1-bin-hadoop2.7 和 Scala 2.11.12。对于 postgres 依赖项,我使用这个版本:
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>9.4-1200-jdbc41</version>
</dependency>
最佳答案
错误消息(对故障排除没有太大帮助)可能不是针对选项dbtable
,而是针对选项url
。
您的 jdbcUrl
似乎缺少 URL 协议(protocol) jdbc:postgresql://
作为前缀。这是一个链接:Spark's JDBC data sources .
关于postgresql - 从 Spark 连接到 Postgres 时出现 NullpointerException - 为什么?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/55616608/